Electrical protective relay



Oct. 9, 1928. 1,686,653

L. N. CRICHTON ELECTRI CAL PROTECTIVE RELAY Filed May 26, 1925 2Sheets-Sheet 1 Fifg:

WI NESSES: 44 43 INVENTOR Wat, [es/A9 4 C'f/Zfi/O/I A TbRNEY L. N.CRICHTON ELECTRICAL PROTECTI VE RELAY Filed May 26, 1923 2 Sheets-Sheet2 r v f:

0000 o ll cydoboo 188 l u a TNESS INVENTDR A e502 /1 (7703/00 ATTO'RNEYPatented Oct. 9, 1928.

UNITED STATES PATENT OFFICE.

LESLIE in. oarcnron, or wmxmsnune, rrnnsrnvmm, assronon 'ro wnsrmonousnELECTRIC a mnnmcrnamo COMPANY, A conromrron or rmmsn- ANIA.

ELECTRICAL PROTECTIVE RELAY.

. g ncauo mea May 26, 1923. Serial in; 641,701.

My invention relates to electrical protective devices and particularlyto protective relays.

" One object of my invention to provide .aprotective relay forsectionalrzing a portion of an electrical system which becomes faulty.

A further object of my invention is to pro vide a relay of the abovecharacter embodying means'whereby-the relay may be continuouslyenengized from the circuit at normal voltage and yet be sensitive atrelat1vely small values of voltage.

A further object of my invention is to provide a relay embodying controlelements that are so arranged as to permit substantially"instantaneousoperation of the relay when the voltage in that portion ofthe circuit at which the relay is disposed decreases to substan-' tiallyzero.

A still further object of my invention is to provide a relay that shallbe positive in operation and rugged in construction, notwithstandingits-sensitivity. c

Figure 1 of theaocompanying drawings is a diagrammatic :view of a'portion of a network illustrating the elemental connections to thesystem, of the relay embodying my invention,

Fig. 2.is a schematic view of therelay embodying my invention andillustrates the relative arrangementof the different parts of the relayand the'connections thereof to the circuit.

Fig. 3 is a perspective view of the relays constructed in accordancewith the principles of my invention.

Fig. 4 is a view, partially in section and partially in elevation, ofthe voltage coil or restraining element.

section, shall operate to isolate that.

,of the current element underj distr ution system, and x Fig. 6-is adiagrammatic view illustrating schematically a modification of the relayembodyin my invention as constructed to provide a irect-ional feature.

In practicing my invention, I provide a.

Fig;.5 is a diagrammatic view of aring current element of the inductiontype similar.

to the induction type overload relays at present employed in protectingelectrical systems. The, disc is arranged to operate through a springupon an arm on a pivoted. lever to causethe lever to close an auxiliarycontrol circuit: A voltage element comprising a voltage coil and movablecore member is arranged to act upon a. second arm connected to thepivoted lever to counteract" the force predetermined normal conditions.

The lever is so balanced that, when the voltage coil is deenergized,very slight movement of the disc will actuate the lever to close theauxiliary control circuit instantaneously. If the voltage coil isenergized, however, the

current element will continue to store energy in the spring disposedbetween the disc and the first moment arm connected to the lever .untilthe force developed in the spring over- 'tacts, which operation isrestrained however,

by the voltage element. The voltage coil actson the core member whichconsists of a small steel elementso proportioned that it saturates at avery low voltage on the coil and the pull upon the core member thereforevaries directly as the voltage on the coil. The time of'operation of therelay,,that is, the time of closing of the auxiliary circuit, varies,therefore, inversely in accordance with the current and directly inaccordance with the voltage. Since the voltage is lowest near the fault,the time of operation depends upon the distance between the relay andthe fault, and, therefore, the relays nearest the fault will operatefirst and those farther away wil re- A gjuire a longer interval of timeto close.

nder such circumstances, the operation of faulty portion of the systemand the other relays will then reset themselves.

In Fig. 1, I have illustrated the manner of connecting the winding ofthe relay to a portion of the circuit between the two substations and11. A. Voltage restrained rclay 12 is provided with a current winding 13and a voltage winding 14 that are differentially effective incontrolling the closing of the contactive device 15 that controls anexternal auxiliary circuit 16 containing the trip coil of an associatedinterrupter.

Upon reference to Figs. 2 and 3 in which the parts of the relay areshown in greater detail, it may be seen that the relay comprises thecurrent element 13, the voltage element 14-, the contactive device 15and a pivoted lever 17 for controlling the operation of the contactivedevice.

The current element 13 comprises a movable induction disc 20, anactuating magnet izable core member 21 which is energized from thecircuit through a current transformer 22. A damping magnet 23 isprovided to restrain somewhat the action of the induction disc and tendsto so control the disc as to cause its angular velocity to besubstantially proportional to the value of the current energizing themagnetizable member 21. The winding of the current element is providedwith a plurality of taps whereby the operating value-0f the element-maybe adjusted for different current values. These taps are illustrated inFig. 3 at the points 24.

The voltage element 14 comprises a coil 26 which is energized from thecircuit through a potential transformer 27. A plurality of resistors 28are provided with means where by one or more of the resistors may beinserted in circuit with the voltage coil. The voltage element com risesfurther a movable core member 30 of magnetic material, preferably steel,having a low magnetic retention and adapted to become saturated whenrelatively lowl values of volt ge are impressed upon the col The coremember 30 is pivoted at a point 31 to the lever arm 17 and the portionof the lever between the point 31 and the pivots 32 may be regarded as amoment arm of the torque developed by the voltage coil for re strainingthe lever 1? from efiecting engagement of the contact members 15.

The lever 17 is also provided with a depending arm 33 which constitutesthe moment arm upon which the force of the current element 13 isimpressed through a spring 34 in such direction as to turn the lever 17to effect engagement or the contact members 15. It will be seen, uponreferring to Fig. 2, that the current element tends to move the arm 33to ward the right-hand side to lower the lefthand end of the lever 17 toeffect engagement of the contact members 15, whereas the voltage elementpulls downwardly upon the rightis interposed between the spring element34 and the arm 33 and disc 20. This construction permits of greaterextent of movement of the current element before the spring 34 isstressed to a great extent.

In the same figure, it will be seen. that the iron case 38 constitutingthe magnetic circuit of the voltage element is provided with a pluralityof flanges or ribs 39 to assist in radiating'the heat that is developedby the voltage coil. Inasmuch as the voltage coil must be sensitive andoperative when energized even to a relatively low degree, such, forexample, as 4% or 5% of normal voltage, it is necessary to provide somemeans for dissipating the heat that is developed by the coil whenenergized by the normal operating voltage.

The construction of the'voltage element may be more readily comprehendedupon reference to Fig. 4 in which the voltage element 14 is illustratedas comprising, in addition to the core member 30 and the surroundingcoil 26-, the cylindrical casing or box 38 of cast iron that constitutespart of the magnet circuit for the coil. The core member 30 that iscontrolled by the voltage coil is supported from a bearing frame 40 inwhich is mounted a jewel screw 41 that is disposed to receive a pin 42that is secured to the end of the lever arm 17. The coil 26, whenenergized, pulls down upon the core member 30 and, through the bearing,the jewel screw pulls down upon the lever 17. The pin and the jewelscrew are adjusted to prevent the bearing frame from slipping oil thepin 42.

The core member 30 is provided with an enlarged portion at its lower end.to decrease the reluctance at that point. A brass pin and washer 44 aresecured to the enlarged portion and cooperate with a stop member 43,that is disposed in the base of the casing 39, to limit the downwardmovement of the core member 30 which is shown in its lowest or attractedposition.

The washer serves to preclude surface-tosurface engagement of theenlarged portion of the core member and the stop 43, and the pin servesto maintain the core member in vertical alinement to preclude frictionalen gagement between the core member and the inner surface'of the coil.It will be noted that the travel of the core member is small.

Normally, the voltage element is calibrated to produce a torque thatwill just exceed the normal torque of the current element and thepivoted lever is maintained in its ineffective position to permit thecontact members to remain open. When the voltage element is entirelydeenergized, it will be seen that very little force, hence very littlemovement, of the current element is necessary to eflect the en gagemcntof the contact member's15 throu h the pivoted lever 17 by reason of therelative y long moment arm.

Between the conditions of complete deenergization of the voltagecoil-and normal energization thereof, thev time interval of operaiton ofthe relay varies between instantaneous operation or zero time element tonon-operation or lnfinlte time element. Since the voltage that will beimpressed on the voltage coil depends upon the distance of the relayfrom the fault. the time element of o eration of the relay will alsodepend upon its istance. The closer the relay is to the fault, the lowerwill be the voltage on the element 14:, and, consequently, the shorterwill be the time element of operation of the relay.

. In Fig. 5 is illustrated a closed or ring system of distribution inconnection with which it is possible to readily ex lain -the applicationof my relay. If a faut should occur at the point A, the relay associatedwith the circuit-interrupting device 50, being the closest to thelocation of the fault, would operate in less time than any of the relaysassociated with the other circuit-interrupting devices and the faultysection would-be disconnected, and isolated by the opening of thecircuit-interrupting device before any of the other relays operated toeffect the opening of the associatedcircuit interrupters. For thisapplicatiomsince energy can flow in only one direction, the singleelement which .I have illustrated'in Figs. 2 and 3 will sufiice.

For portions of the circuit within the ring, however, it is necessary toprovide a. relay that will take into consideration not only the distanceof th particular relay from the location of the faulty condition butalso the direc- -tion in which energy is flowing towardythe faultycondition. If, for example, the por- "tion of the system between thesubstations 54 and 55 be considered, it will be seen that, upon theoccurence of a fault in that portion of the system at the point B,energy will flow to the fault through the substation 54 and also aroundthrough the right-hand portion of the ringthrough the substation 55.Since the substation 54 is provided with two circuitinterrupting devices56 and 57 and the substation 55 is provided with two circuitinterruptingdevices 58 and 59, it is essential that some selective means beprovidedto control the operation of the proper circuit interrupters inaccordance wlth the direction of energy flow to the fault. Forapplications to systems of this type, I provide a relay struc- ,ture, asillustrated schematically in Fig. 6-,

which embodies, in addition to the voltage restrained element 12previously described, a directional element 60 that is similar to thatemployed in reverse power relays, such as illustrated and described inPatent No. 1,365,228, issued Jan. 11, 1921-, t0 B. H. Smith.

The contacts 61 of the directional element are arranged to close acircuit in series with the contacts 15 ofthe voltage-restrained eleme ntfor tripping the circuit-interrupter 62. The directional elements of therelays associ:

ated with the interrupters 57 and 58 are arranged to close their contactmembers only when energy flows fromv the substationslinto the sectionconnecting the stations. Thus, upon the occurence of a fault in thesections between the stations 54 and 55, the voltagerestrainedelementsof the relays associated with both of the interrupters 56 and 57would operate to close their contact members at the same time after aninterval depending upon the distance of the station 54 from the fault.

Similarly, the voltage-restrained elements associated with the circuitinterrupters 58 and 59 would operate to close their respective contactmembers at the same time after an interopen to isolate the faultysection between the stations 54; and 55, leaving the stations 5& and 55connected to the system.

, My invention thus comprehcnds a relay device that shall operate toclose its contact members after an interval of time that is proportionalto its distance from the location of a fault when a faulty conditionoccurs in the system. By such means, I am able to isolate only thefaulty section and to permit the remainder of the system to continue totransmit energy.

My invention is not limited to the specific arrangements that l haveillustrated, hut may be variously modified without departing from thespirit and scope thereof, as set forth in the appended claims.

'1 claim as my invention 2 1. in an electrical system, a protectiverelay embodyingtwo operating coils energized from the circuit and meansfor counterbalancing their effects comprising a pivoted lever contact,an induction disc subject to the influence of one coil for controllingthe lever in one direction and a movable restraining member subject tothe influence of the other coil for opposing the operation of the lever.

2. A protective relay comprising a pivoted lever, a contactive devicecontrolled thereby, an induction meter element and a spring con- 7spring controlled by the induction element and operative to exert agradually increasing torque upon the lever through the depending arm,and a counteracting element comprising a coil and a movable core membersubject to the influence of the coil for determining the time elapsingbefore the,

lever is actuated.

4. A protective relay comprising a pivoted lever, 21 contactive devicecontrolled thereby, an induction meter element, means constituting twomoment arms for controlling the lever, energy-storing means disposedbetween the induct1on element and one arm tending to exert a varyingtorque on the lever, and means controlling the other arm tending torestrain operation of the contact member until the torque on said leverexceeds a certain value.

5. In an electric circuit, a protective relay embodying a pivoted lever,a contactive device controlled thereby, two members constituting momentarms o'tthe lever, a current-controlled element connected to one momentarm to control the movement of the lever, a voltage-controlledrestraining element connected to the other arm and operative to preventactuation of the lever under certain conditions and means for energizingsaid elements in accordance with the current and voltage of the circuit,respectively.

6. In an electric circuit, a protective relay embodying a pivoted lever,21 contactive device thereon, two members constituting moment arms forthe lever, a current element, a spring controlled thereby forcontrolling one moment arm, a voltage restraining element on the otherarm acting counter to the current element and means for energizing saidelements 1n accordance With the current and voltage of the circuit,respectively.

7 In an electrical system, the combination tactive device controlledthereby, a spiral spring controlled by the induction current element forgradually impressing an actuating force on the lever tending to operatethe contactivedevice and means subject to the control of the solenoidfor varying the time of operation of the lever; the pivoted lever, theinduction element and the solenoid being so balanced that slightmovement of the induction element Will operate the contactive' devicewhen the solenoid is not energized.

' 8. A protective relay energized from the circuit comprising acontactive device, an induction element energized in accordance with thecurrent in the circuit, a spiral spring between said element and saidcontactive device, and a voltage element energized in accordance withthe circuit voltage and disposed to restrain the operation of thecontactive device until the tension' in said spring exceeds a certainvalue.

9. In combination with an electric circuit having a definite normalvoltage, a relay comprising contact members, means including a pivotedinduction-meter element for exerting a gradually increasing torquetending to close said contact members when the current in said circuitexceeds a predetermined value and restraining means energized in accordance with the voltage of said circuit for preventing the closure thereofuntil a sufiicient torque is exerted, said restraining means comprisinga 'magnetizable core member that is saturated at a relatively lowvoltage and electromagnetic means tending to hold the same against astationary stop. a

In testimony whereof, I have hereunto subscribed my name this 19th da ofMay, 1923.

LESLIE N. RICHTON.

